Research On Processing Technology Of Lactic Acid Bacteria Synergistically Ferment Kiwi Fruit Vinegar

China’s kiwifruit planting area and output rank first in the world.Kiwifruit is easy to produce a large number of other fruits in the production,processing and grading process,and if it is not handled properly,it is easy to cause waste of resources and environmental pollution.Although these exotic fruits are not commercial,they are good raw materials for brewing fruit vinegar because they are rich in sugars and organic acids.The fermentation of traditional fruit vinegar is mainly liquid fermentation,which leads to poor taste and flavor of fruit vinegar due to the single raw materials and fermentation strains.In this experiment,kiwifruit and other exotic fruits were used as raw materials,and the fermentation method and process conditions of kiwifruit vinegar were optimized by using lactic acid bacteria synergistic yeast and acetic acid bacteria to ferment kiwifruit vinegar,so as to provide a basis for the processing of highquality kiwifruit vinegar.The main findings are as follows:(1)The sensory quality of fruit vinegar was analyzed by using electronic nose,electronic tongue technology and sensory score,and the results showed that the sensory quality of kiwifruit vinegar under different fermentation methods was different,and the fruit vinegar fermented by Lactobacillus plantarum and then yeast and acetic acid bacteria fermented had the highest sensory score.(2)The effects of different fermentation methods on the volatile components of kiwifruit vinegar were analyzed by headspace solid phase microextraction-gas chromatography-mass chromatography-mass spectrometry(SPME-GC-MS).The results showed that the cofermentation of lactic acid bacteria could increase the content of volatile components in kiwifruit fruit vinegar,including esters,ketones,aldehydes,phenols and alcohols.A total of36 volatile components were identified from kiwi fruit vinegar,including 8 esters,4 ketones,5 acids,8 aldehydes,2 phenols,8 alcohols and 1 other compound.Kiwifruit vinegar fermented first by Lactobacillus plantarum and then fermented by yeast and acetic acid bacteria had the largest variety of volatile components(23 species).(3)High performance liquid chromatography(HPLC)was used to analyze the effects of different fermentation methods on organic acid of kiwifruit vinegar.The organic acid content of kiwifruit vinegar under the synergistic fermentation method of different lactic acid bacteria was different,but acetic acid and lactic acid were the main ones,and inoculation of lactic acid bacteria could increase the lactic acid content in kiwifruit fruit vinegar.(4)The physical and chemical indexes of kiwifruit vinegar co-fermented by lactic acid bacteria were determined.The results showed that after the synergistic fermentation of lactic acid bacteria,the alcohol content of fruit wine,the total phenolic content and vitamin C content of fruit vinegar,and the total flavonoid content and DPPH free radical scavenging rate of fruit vinegar were increased.Fruit vinegar fermented by Lactobacillus plantarum and then yeast and acetic acid bacteria had the highest total phenolic content(18.64 mg/m L),strong free scavenging ability of DPPH free radicals and ABTS(77.54% and 67.58%,respectively),and higher contents of total flavonoids and vitamin C(0.48 mg/m L and 2.21 mg/m L,respectively).(5)Combined with sensory evaluation,volatile components,organic acids and physical and chemical indexes,the method of fermentation of Lactobacillus plantarum and then yeast and acetic acid bacteria was selected for process optimization.The results showed that the main order affecting the total acid content of fruit vinegar was as follows: alcohol content >acetic acid bacteria inoculation amount > temperature,and the primary order affecting sensory score was acetic acid bacteria inoculation amount > temperature > alcohol.Combining the two indicators,the optimal process conditions were: lactic acid bacteria inoculation rate of 5%,yeast inoculation amount of 0.02%,initial alcohol content 9% vol,acetic acid bacteria inoculation amount of 3%,acetic acid bacteria fermentation temperature of 32 °C,under this optimal process,the total acid content measured was 44.67 g/L,and the sensory score was93.44.In summary,the collaborative fermentation of lactic acid bacteria can increase the volatile component content,lactic acid content,total flavonoid content and DPPH free radical scavenging rate of kiwi fruit vinegar.Among them,kiwifruit vinegar fermented by Lactobacillus plantarum and yeast and acetic acid bacteria had the largest variety of volatile components(23 kinds),the highest total phenolic content was 18.64 mg/m L,the DPPH scavenging ability was the strongest 77.54%,ABTS has a strong ability to scavenge free radicals 67.58%,and the content of total flavonoids,lactic acid and vitamin C were higher,which were 0.48 mg/m L,2.99 mg/m L and 2.21 mg/m L,respectively.Through process optimization,the best process of co-fermentation of kiwifruit vinegar by lactic acid bacteria was obtained,which could provide theoretical basis and technical support for the processing of kiwifruit vinegar.